Ghrelin inhibits LPS-induced release of IL-6 from mouse dopaminergic neurones

GHS-R1a deficiency protects against lipopolysaccharide-induced spatial memory impairment in mice

Neuroinflammation has been implicated in cognitive deficits of neurological and neurodegenerative diseases. There is abundant evidence that the application of ghrelin, an orexigenic hormone regulating appetite and energy balance, abrogates neuroinflammation and rescues associated memory impairment. However, the underlying mechanism is uncertain. In this study, we find that both intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) administration of lipopolysaccharide (LPS) impairs spatial memory in mice. LPS treatment causes neuroinflammation and microglial activation in the hippocampus. Ghsr1a deletion suppresses LPS-induced microglial activation and neuroinflammation, and rescued LPS-induced memory impairment. Our findings thus suggest that GHS-R1a signaling may promote microglial immunoactivation and contribute to LPS-induced neuroinflammation. GHS-R1a may be a new therapeutic target for cognitive dysfunction associated with inflammatory conditions.

Ghrelin system in Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia in seniors. Current efforts to understand the etiopathogenesis of this neurodegenerative disorder have brought forth questions about systemic factors in the development of AD. Ghrelin is a brain-gut peptide that is activated by ghrelin O-acyltransferase (GOAT) and signals via its receptor, growth hormone secretagogue receptor (GHSR). With increasing recognition of the neurotropic effects of ghrelin, the role of ghrelin system deregulation in the development of AD has been accentuated in recent years. In this review, we summarized recent research progress regarding the mechanisms of ghrelin signaling dysregulation and its contribution to AD brain pathology. In addition, we also discussed the therapeutic potential of strategies targeting ghrelin signaling for the treatment of this neurological disease.

Liver-expressed antimicrobial peptide 2 functions independently of growth hormone secretagogue receptor in calorie-restricted mice

Ghrelin is a gastric-derived peptide that stimulates feeding, blood glucose elevation, body temperature reduction, and growth hormone (GH) secretion. Liver-expressed antimicrobial peptide 2 (LEAP2) is an endogenous antagonist of the ghrelin receptor, also called growth hormone secretagogue receptor (GHSR). We studied the effects of LEAP2 administration on feeding, body weight, glycemia, body temperature, and inflammation-related genes in the liver in C57BL/6 J mice and Ghsr-knockout (Ghsr-KO) mice. We found that a single administration of LEAP2 did not abolish fasting-induced food intake in 24-h fasted C57BL/6 J mice or Ghsr-KO mice. Moreover, continuous LEAP2 administration to mice fed ad libitum for 6 days did not affect feeding, body temperature, plasma ghrelin, or blood glucose. By contrast, continuous LEAP2 administration to calorie-restricted C57BL/6 J mice and Ghsr-KO mice induced body weight loss, hypoglycemia, body temperature reduction, and upregulation of Il-6 and Il-1β mRNAs in the liver. Our findings suggest that LEAP2 functions independently of GHSR, implying that LEAP2 affects physiology beyond the ghrelin-GHSR system.

Ghrelin Acylation-A Post-Translational Tuning Mechanism Regulating Adult Hippocampal Neurogenesis

Adult hippocampal neurogenesis—the generation of new functional neurones in the adult brain—is impaired in aging and many neurodegenerative disorders. We recently showed that the acylated version of the gut hormone ghrelin (acyl-ghrelin) stimulates adult hippocampal neurogenesis while the unacylated form of ghrelin inhibits it, thus demonstrating a previously unknown function of unacyl-ghrelin in modulating hippocampal plasticity. Analysis of plasma samples from Parkinson’s disease patients with dementia demonstrated a reduced acyl-ghrelin:unacyl-ghrelin ratio compared to both healthy controls and cognitively intact Parkinson’s disease patients. These data, from mouse and human studies, suggest that restoring acyl-ghrelin signalling may promote the activation of pathways to support memory function. In this short review, we discuss the evidence for ghrelin’s role in regulating adult hippocampal neurogenesis and the enzymes involved in ghrelin acylation and de-acylation as targets to treat mood-related disorders and dementia.

Ghrelin alleviates 6-hydroxydopamine-induced neurotoxicity in SH-SY5Y cells

Ghrelin is a neuropeptide that has various physiological functions and has been demonstrated to be neuroprotective in a number of neurological disease models. However, the underlying mechanisms of ghrelin in Parkinson’s disease remain largely unexplored. The current study aimed to study the effects of ghrelin in a 6-hydroxydopamine (6-OHDA)-induced Parkinson’s disease model and evaluate the potential underlying mechanisms. In the present study, we treated an SH-SY5Y cell model with 6-OHDA, and observed that pretreatment with different concentrations of ghrelin (1, 10, and 100 nM) for 30 minutes relieved the neurotoxic effects of 6-OHDA, as revealed by Cell Counting Kit-8 and Annexin V/propidium iodide (PI) apoptosis assays. Reverse transcription quantitative polymerase chain reaction and western blot assay results demonstrated that 6-OHDA treatment upregulated α-synuclein and lincRNA-p21 and downregulated TG-interacting factor 1 (TGIF1), which was predicted as a potential transcription regulator of the gene encoding α-synuclein (SNCA). Ghrelin pretreatment was able to reverse the trends caused by 6-OHDA. The Annexin V/PI apoptosis assay results revealed that inhibiting either α-synuclein or lincRNA-p21 expression with small interfering RNA (siRNA) relieved 6-OHDA-induced cell apoptosis. Furthermore, inhibiting lincRNA-p21 also partially upregulated TGIF1. By retrieving information from a bioinformatics database and performing both double luciferase and RNA immunoprecipitation assays, we found that lincRNA-p21 and TGIF1 were able to form a double-stranded RNA-binding protein Staufen homolog 1 (STAU1) binding site and further activate the STAU1-mediated mRNA decay pathway. In addition, TGIF1 was able to transcriptionally regulate α-synuclein expression by binding to the promoter of SNCA. The Annexin V/PI apoptosis assay results showed that either knockdown of TGIF1 or overexpression of lincRNA-p21 notably abolished the neuroprotective effects of ghrelin against 6-OHDA-induced neurotoxicity. Collectively, these findings suggest that ghrelin exerts neuroprotective effects against 6-OHDA-induced neurotoxicity via the lincRNA-p21/TGIF1/α-synuclein pathway.

Potential Antioxidative, Anti-inflammatory and Immunomodulatory Effects of Ghrelin, an Endogenous Peptide from the Stomach in SARS-CoV2 Infection

The current COVID-19 pandemic is one of the most devastating events in recent history. The respiratory effects of this disease include acute respiratory distress syndrome, systemic inflammation, cytokine storm, and pulmonary fibrosis. Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor, is a peptide hormone secreted mainly by the stomach. Interestingly, ghrelin possesses promising antioxidant, anti-and inflammatory effects, making it an attractive agent to reduce the complications of the SARS-CoV-2. In addition, ghrelin exerts a wide range of immunomodulatory and anti-inflammatory effects and can mitigate the uncontrolled cytokine production responsible for acute lung injury by upregulating PPARγ and down-regulating NF-κB expression. Ghrelin has also been reported to enhance Nrf2 expression in inflammatory conditions which led to the suppression of oxidative stress. The current opinion summarizes the evidence for the possible pharmacological benefits of ghrelin in the therapeutic management of SARS-CoV-2 infection.

Ghrelin as an Anti-Sepsis Peptide: Review

Sepsis continues to produce widespread inflammation, illness, and death, prompting intensive research aimed at uncovering causes and therapies. In this article, we focus on ghrelin, an endogenous peptide with promise as a potent anti-inflammatory agent. Ghrelin was discovered, tracked, and isolated from stomach cells based on its ability to stimulate release of growth hormone. It also stimulates appetite and is shown to be anti-inflammatory in a wide range of tissues. The anti-inflammatory effects mediated by ghrelin are a result of both the stimulation of anti-inflammatory processes and an inhibition of pro-inflammatory forces. Anti-inflammatory processes are promoted in a broad range of tissues including the hypothalamus and vagus nerve as well as in a broad range of immune cells. Aged rodents have reduced levels of growth hormone (GH) and diminished immune responses; ghrelin administration boosts GH levels and immune response. The anti-inflammatory functions of ghrelin, well displayed in preclinical animal models of sepsis, are just being charted in patients, with expectations that ghrelin and growth hormone might improve outcomes in patients with sepsis.

Early low-dose ghrelin intervention via miniosmotic pumps could protect against the progressive dopaminergic neuron loss in Parkinson's disease mice

Ghrelin has been identified as a multifunctional peptide that has a potential application for treating Parkinson's disease (PD). The objective of this study was to assess the effects of subcutaneous administration of low-dose ghrelin via miniosmotic pumps on PD progression. The decreased levels of total and active ghrelin in plasma were rescued by ghrelin administration in PD mice. Interestingly, ghrelin did not affect weight gain in wild-type mice but improved weight loss in PD mice. We observed the attenuation of dopaminergic neuron loss in substantia nigra and a low level of dopamine content in the striatum in PD mice with ghrelin treatment. Ghrelin administration could improve the microenvironment of dopaminergic neurons by inhibiting microglial proliferation and proinflammatory cytokine expression and could enhance cell survival by upregulating Bcl-2/Bax ratio and superoxide dismutase1 protein level in the substantia nigra of PD mice. Subcutaneous administration of low-dose ghrelin could prevent the onset of the progression of PD and also provide a possible method for ghrelin application to cure PD.

Acylated Ghrelin as a Multi-Targeted Therapy for Alzheimer's and Parkinson's Disease

Much thought has been given to the impact of Amyloid Beta, Tau and Alpha-Synuclein in the development of Alzheimer's disease (AD) and Parkinson's disease (PD), yet the clinical failures of the recent decades indicate that there are further pathological mechanisms at work. Indeed, besides amyloids, AD and PD are characterized by the culminative interplay of oxidative stress, mitochondrial dysfunction and hyperfission, defective autophagy and mitophagy, systemic inflammation, BBB and vascular damage, demyelination, cerebral insulin resistance, the loss of dopamine production in PD, impaired neurogenesis and, of course, widespread axonal, synaptic and neuronal degeneration that leads to cognitive and motor impediments. Interestingly, the acylated form of the hormone ghrelin has shown the potential to ameliorate the latter pathologic changes, although some studies indicate a few complications that need to be considered in the long-term administration of the hormone. As such, this review will illustrate the wide-ranging neuroprotective properties of acylated ghrelin and critically evaluate the hormone's therapeutic benefits for the treatment of AD and PD.

Correlations between immune and metabolic serum markers and schizophrenia/bipolar disorder polygenic risk score in first-episode psychosis

AIMS

There is a strong interest in identifying the biological mechanisms involved in the genetic risk for psychotic disorders. In this study, we evaluated the correlation between serum concentrations of specific molecular markers and the genetic component for schizophrenia and bipolar disorder.

METHODS

We analysed the association between the polygenic risk score (PRS) and the serum levels of different inflammatory/metabolic markers in a sample of 81 first-episode psychosis patients (FEP) with a diagnosis of schizophrenia or bipolar disorder and 33 controls.

RESULTS

A positive correlation of schizophrenia and bipolar disorder PRS with the inflammatory marker C-C Motif Chemokine Ligand 4 serum concentration (ρ = 0.42, P = 1.56 × 10^-04 and ρ = 0.40, P = 1.65 × 10^-03 , respectively) and a negative correlation with the serum ghrelin content (ρ = - 0.35, P = 4.27 × 10^-03 and ρ = - 0.45, P = 6.05 × 10^-04 , respectively) were observed.

CONCLUSION

These findings provide new insight into the biological underpinnings of the PRS component, thus supporting a role of the genetic liability on the inflammatory and metabolic alterations that characterize psychosis onset.

From obesity through gut microbiota to cardiovascular diseases: a dangerous journey

The co-existence of humans and gut microbiota started millions of years ago. Until now, a balance gradually developed between gut bacteria and their hosts. It is now recognized that gut microbiota are key to form adequate immune and metabolic functions and, more in general, for the maintenance of good health. Gut microbiota are established before birth under the influence of maternal nutrition and metabolic status, which can impact the future metabolic risk of the offspring in terms of obesity, diabetes, and cardiometabolic disorders during the lifespan. Obesity and diabetes are prone to disrupt the gut microbiota and alter the gut barrier permeability, leading to metabolic endotoxaemia with its detrimental consequences on health. Specific bacterial sequences are now viewed as peculiar signatures of the metabolic syndrome across life stages in each individual, and are linked to pathogenesis of cardiovascular diseases (CVDs) via metabolic products (metabolites) and immune modulation. These mechanisms have been linked, in association with abnormalities in microbial richness and diversity, to an increased risk of developing arterial hypertension, systemic inflammation, nonalcoholic fatty liver disease, coronary artery disease, chronic kidney disease, and heart failure. Emerging strategies for the manipulation of intestinal microbiota represent a promising therapeutic option for the prevention and treatment of CVD especially in individuals prone to CV events.

Targeting of G-protein coupled receptors in sepsis

The Third International Consensus Definitions (Sepsis-3) define sepsis as life-threatening multi-organ dysfunction caused by a dysregulated host response to infection. Sepsis can progress to septic shock-an even more lethal condition associated with profound circulatory, cellular and metabolic abnormalities. Septic shock remains a leading cause of death in intensive care units and carries a mortality of almost 25%. Despite significant advances in our understanding of the pathobiology of sepsis, therapeutic interventions have not translated into tangible differences in the overall outcome for patients. Clinical trials of antagonists of various pro-inflammatory mediators in sepsis have been largely unsuccessful in the past. Given the diverse physiologic roles played by G-protein coupled receptors (GPCR), modulation of GPCR signaling for the treatment of sepsis has also been explored. Traditional pharmacologic approaches have mainly focused on ligands targeting the extracellular domains of GPCR. However, novel techniques aimed at modulating GPCR intracellularly through aptamers, pepducins and intrabodies have opened a fresh avenue of therapeutic possibilities. In this review, we summarize the diverse roles played by various subfamilies of GPCR in the pathogenesis of sepsis and identify potential targets for pharmacotherapy through these novel approaches.

Spinal cord injury and the human microbiome: beyond the brain-gut axis

In addition to standard management for the treatment of the acute phase of spinal cord injury (SCI), implementation of novel neuroprotective interventions offers the potential for significant reductions in morbidity and long-term health costs. A better understanding of the systemic changes after SCI could provide insight into mechanisms that lead to secondary injury. An emerging area of research involves the complex interplay of the gut microbiome and the CNS, i.e., a brain-gut axis, or perhaps more appropriately, a CNS-gut axis. This review summarizes the relevant literature relating to the gut microbiome and SCI. Experimental models in stroke and traumatic brain injury demonstrate the bidirectional communication of the CNS to the gut with postinjury dysbiosis, gastrointestinal-associated lymphoid tissue-mediated neuroinflammatory responses, and bacterial-metabolite neurotransmission. Similar findings are being elucidated in SCI as well. Experimental interventions in these areas have shown promise in improving functional outcomes in animal models. This commensal relationship between the human body and its microbiome, particularly the gut microbiome, represents an exciting frontier in experimental medicine.

Ghrelin promotes midbrain neural stem cells differentiation to dopaminergic neurons through Wnt/β-catenin pathway

Ghrelin plays a neuroprotective role in the process of dopaminergic (DAergic) neurons degeneration in Parkinson's disease (PD). However, it still largely unknown whether ghrelin could affect the midbrain neural stem cells (mbNSCs) from which DAergic neurons are originated. In the present study, we observed that ghrelin enhanced mbNSCs proliferation, and promoted neuronal differentiation especially DAergic neuron differentiation both in vitro and ex vivo. The messenger RNA levels of Wnt1, Wnt3a, and glial cell line-derived neurotrophic factor were increased in response to the ghrelin treatment. Results showed that Wnt/β-catenin pathway was relevant to this DAergic neuron differentiation induced by ghrelin. Our finding gave a new evidence that ghrelin may enable clinical therapies for PD by its neurogenesis role.

Ghrelin in Alzheimer's disease: Pathologic roles and therapeutic implications

Ghrelin, which has many important physiological roles, such as stimulating food intake, regulating energy homeostasis, and releasing insulin, has recently been studied for its roles in a diverse range of neurological disorders. Despite the several functions of ghrelin in the central nervous system, whether it works as a therapeutic agent for neurological dysfunction has been unclear. Altered levels and various roles of ghrelin have been reported in Alzheimer's disease (AD), which is characterized by the accumulation of misfolded proteins resulting in synaptic loss and cognitive decline. Interestingly, treatment with ghrelin or with the agonist of ghrelin receptor showed attenuation in several cases of AD-related pathology. These findings suggest the potential therapeutic implications of ghrelin in the pathogenesis of AD. In the present review, we summarized the roles of ghrelin in AD pathogenesis, amyloid beta (Aβ) homeostasis, tau hyperphosphorylation, neuroinflammation, mitochondrial deficit, synaptic dysfunction and cognitive impairment. The findings from this review suggest that ghrelin has a novel therapeutic potential for AD treatment. Thus, rigorously designed studies are needed to establish an effective AD-modifying strategy.

Ghrelin attenuates oxidative stress and neuronal apoptosis via GHSR-1α/AMPK/Sirt1/PGC-1α/UCP2 pathway in a rat model of neonatal HIE

Neuronal apoptosis induced by oxidative stress is one of the major pathological processes involved in neurological impairment after hypoxic-ischemic encephalopathy (HIE). Ghrelin, the unique endogenous ligand for the growth hormone secretagogue receptor-1α (GHSR-1α), could take an anti-apoptotic role in the brain. However, whether ghrelin can attenuate neuronal apoptosis by attenuating oxidative stress after hypoxia-ischemia (HI) insult remains unknown. To investigate the beneficial effects of ghrelin on oxidative stress injury and neuronal apoptosis induced by HI, ten-day old unsexed rat pups were subjected to HI injury and exogenous recombinant human ghrelin(rh-Ghrelin) was administered intranasally at 1 h and 24 h after HI induction. [D-Lys³]-GHRP-6, a selective inhibitor of GHSR-1α and Ex527, a selective inhibitor of GHSR-1α were administered intranasally at 1 h before HI induction respectively. Small interfering ribonucleic acid (siRNA) for GHSR-1α were administered by intracerebroventricular (i.c.v) injection at 24 h before HI induction. Neurological tests, immunofluorescence, MitoSox staining, Fluoro-Jade C staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and western blot experiments were performed. Our results indicated that ghrelin significantly improved neurobehavioral outcomes and reduced oxidative stress and neuronal apoptosis. Moreover, ghrelin treatment significantly promoted phosphorylation of AMPK, upregulated the expression of Sirt1, PGC-1α, UCP2 and the ratio of Bcl2/Bax, while it downregulated cleaved caspase-3 levels. The protective effects of ghrelin were reversed by [D-Lys³]-GHRP-6, GHSR-1α siRNA or Ex527. In conclusion, our data demonstrated that ghrelin reduced oxidative stress injury and neuronal apoptosis which was in part via the GHSR-1α/AMPK/Sirt1/PGC-1α/UCP2 signalling pathway after HI. Ghrelin may be a novel therapeutic target for treatment after neonatasl HI injury.

Neuroprotective Effects of Brain-Gut Peptides: A Potential Therapy for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and is typically associated with progressive motor and non-motor dysfunctions. Currently, dopamine replacement therapy is mainly used to relieve the motor symptoms, while its long-term application can lead to various complications and does not cure the disease. Numerous studies have demonstrated that many brain-gut peptides have neuroprotective effects in vivo and in vitro, and may be a promising treatment for PD. In recent years, some progress has been made in studies on the neuroprotective effects of some newly-discovered brain-gut peptides, such as glucagon-like peptide 1, pituitary adenylate cyclase activating polypeptide, nesfatin-1, and ghrelin. However, there is still no systematic review on the neuroprotective effects common to these peptides. Thus, here we review the neuroprotective effects and the associated mechanisms of these four peptides, as well as other brain-gut peptides related to PD, in the hope of providing new ideas for the treatment of PD and related clinical research.

Dopamine neuronal protection in the mouse Substantia nigra by GHSR is independent of electric activity

Objective

Dopamine neurons in the Substantia nigra (SN) play crucial roles in control of voluntary movement. Extensive degeneration of this neuronal population is the cause of Parkinson's disease (PD). Many factors have been linked to SN DA neuronal survival, including neuronal pacemaker activity (responsible for maintaining basal firing and DA tone) and mitochondrial function. Dln-101, a naturally occurring splice variant of the human ghrelin gene, targets the ghrelin receptor (GHSR) present in the SN DA cells. Ghrelin activation of GHSR has been shown to protect SN DA neurons against 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) treatment. We decided to compare the actions of Dln-101 with ghrelin and identify the mechanisms associated with neuronal survival.

Methods

Histologial, biochemical, and behavioral parameters were used to evaluate neuroprotection. Inflammation and redox balance of SN DA cells were evaluated using histologial and real-time PCR analysis. Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology was used to modulate SN DA neuron electrical activity and associated survival. Mitochondrial dynamics in SN DA cells was evaluated using electron microscopy data.

Results

Here, we report that the human isoform displays an equivalent neuroprotective factor. However, while exogenous administration of mouse ghrelin electrically activates SN DA neurons increasing dopamine output, as well as locomotion, the human isoform significantly suppressed dopamine output, with an associated decrease in animal motor behavior. Investigating the mechanisms by which GHSR mediates neuroprotection, we found that dopamine cell-selective control of electrical activity is neither sufficient nor necessary to promote SN DA neuron survival, including that associated with GHSR activation. We found that Dln101 pre-treatment diminished MPTP-induced mitochondrial aberrations in SN DA neurons and that the effect of Dln101 to protect dopamine cells was dependent on mitofusin 2, a protein involved in the process of mitochondrial fusion and tethering of the mitochondria to the endoplasmic reticulum.

Conclusions

Taken together, these observations unmasked a complex role of GHSR in dopamine neuronal protection independent on electric activity of these cells and revealed a crucial role for mitochondrial dynamics in some aspects of this process.

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Dln101 is a human splice-variant of the ghrelin gene with different expression pattern.

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Ghrelin and Dln101 display equivalent levels of neuroprotection of SN DA cells.

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Modulation of electrical activity of SN DA cells is not relevant for neuroprotection.

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Mitochondrial fusion protein 2 (MFN 2) blocks DLN101-induced mitochondrial fusion in SN DA neurons and prevents DLN101-induced neuroprotection.

Intestinal barrier dysfunction following traumatic brain injury

Traumatic brain injury (TBI) can cause non-neurological injuries to other organs such as the intestine. Newer studies have shown that paracellular hyperpermeability is the basis of intestinal barrier dysfunction following TBI. Ischemia-reperfusion injury, inflammatory response, abnormal release of neurotransmitters and hormones, and malnutrition contribute to TBI-induced intestinal barrier dysfunction. Several interventions that may protect intestinal barrier function and promote the recovery of TBI have been proposed, but relevant studies are still limited. This review is to clarify the established mechanisms of intestinal barrier dysfunction following TBI and to describe the possible strategies to reduce or prevent intestinal barrier dysfunction.

Comprehensive biology of antipyretic pathways

Pyrogens, the fever inducing substances accidently enter into a human body through contamination from medical or pharmaceutical products may create mild to severe complications including septicaemia and shocking syndromes. To avoid such drastic situations all the pharmaceuticals and medical devices are analysed for presence of pyrogens prior to their release into market. The entry of exogenous pyrogens like bacterial endotoxins induces the release of endogenous pyrogens or inflammatory cytokines that activate immune system to defend against these pathogens. Generation of heat is considered as one of the important defence mechanism of body achieved through receptor mediated interaction of endogenous pyrogens at the thermoregulatory centre of hypothalamus. However, uncontrolled fever and febrile reaction may cause lethal effects to the subject itself. So a well sophistically functioning antipyretic mechanism is necessary to achieve thermoregulation. The coordinated interaction of antipyretic cytokines and other mediators are active in human immune system which play a crucial role in maintaining thermal homeostasis. The multiple interacting antipyretic signals and their mechanism are the major subjects of this review.

Effects of Ghrelin on the Apoptosis of Rheumatoid Arthritis Fibroblast-Like Synoviocyte MH7A Cells

Ghrelin is a circulating peptide hormone, which involved in promoting feeding and regulating energy metabolism in human and rodents. Abnormal synovial hyperplasia is the most important pathologic hallmark of rheumatoid arthritis (RA), which is characterised by tumor-like expansion. Existing studies indicated that there may exist some relation between the decreased ghrelin and the abnormally proliferating synovial cells in RA. Therefore, the aim of this study is to explore the apoptotic effects of ghrelin on MH7A synovial cells in vitro. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the effects of ghrelin on the viability of MH7A cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) and flow cytometry were used to test the apoptotic effects of ghrelin. At last, Western blot and real-time PCR were performed to explore the expression of caspases-8, -9, and -3 after the treatment of ghrelin. MTT experiments showed that ghrelin could inhibit viability of MH7A cells. The results of flow cytometry and TUNEL showed that ghrelin could induce apoptosis of MH7A synovial cells. Western blot showed that expression of cleaved-caspases-8, -9, and -3 were increased in ghrelin stimulation group compared with the control group, while expression of pro-caspases-8, -9, and -3 had no significant difference. In mRNA levels, ghrelin can decrease pro-caspases-8, -9, and -3 mRNA expression, which confirmed the results of protein levels. Then these apoptotic effects were significantly reversed by [D-Lys₃] GHRP-6 (ghrelin receptor antagonist). This study found that ghrelin can induce apoptosis of MH7A cells through caspase signaling pathways.

The Impact of Ghrelin on the Survival and Efficacy of Dopaminergic Fetal Grafts in the 6-OHDA-Lesioned Rat

Ghrelin is a peptide produced in the gut with a wide range of physiological functions. Recent studies have suggested it may have potential as a neuroprotective agent in models of Parkinson's disease, reducing the impact of toxic challenges on the survival of nigral dopaminergic neurons. The presence of the ghrelin receptor (GHSR1a) on the dopaminergic neurons of the substantia nigra raises the possibility that a potential application for this property of ghrelin may be as an adjunctive neuroprotective agent to enhance and support the survival and integration of dopaminergic cells transplanted into the striatum. Thus far, inconsistent outcomes in clinical trials for fetal cell transplantation have been linked to low rates of cell survival which we hypothesize could be ameliorated by the presence of ghrelin. To explore this, we confirmed the expression of the GHSR1a and related enzymes on e14 ventral mesencephalon. To determine a functional effect, five groups of female Sprague-Dawley rats received a unilateral 6-OHDA lesion to the medial forebrain bundle and four received an intrastriatal graft of e14 ventral mesencephalic cells. Grafted rats received saline; acyl-ghrelin (10 µg/kg); acyl-ghrelin (50 µg/kg) or the ghrelin agonist JMV-2894 (160 µg/kg) i.p. for 8 weeks. An effect of ghrelin at low dose on hippocampal neurogenesis indicated blood-brain barrier penetrance and attainment of biologically relevant levels but neither acyl-ghrelin nor JMV-2894 improved graft survival or efficacy.

Modulation of M1/M2 polarization by capsaicin contributes to the survival of dopaminergic neurons in the lipopolysaccharide-lesioned substantia nigra in vivo

The present study examined the neuroprotective effects of capsaicin (CAP) and explored their underlying mechanisms in a lipopolysaccharide (LPS)-lesioned inflammatory rat model of Parkinson’s dieases (PD). LPS was unilaterally injected into the substantia nigra (SN) in the absence or presence of CAP or capsazepine (CZP, a TRPV1 antagonist). The SN tissues were prepared for immunohistochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, western blot analysis, blood–brain barrier (BBB) permeability evaluation, and reactive oxygen species (ROS) detection. We found that CAP prevented the degeneration of nigral dopamine neurons in a dose-dependent manner and inhibited the expression of proinflammatory mediators in the LPS-lesioned SN. CAP shifted the proinflammatory M1 microglia/macrophage population to an anti-inflammatory M2 state as demonstrated by decreased expression of M1 markers (i.e., inducible nitric oxide synthase; iNOS and interleukin-6) and elevated expression of M2 markers (i.e., arginase 1 and CD206) in the SN. RT-PCR, western blotting, and immunohistochemical analysis demonstrated decreased iNOS expression and increased arginase 1 expression in the CAP-treated LPS-lesioned SN. Peroxynitrate production, reactive oxygen species levels and oxidative damage were reduced in the CAP-treated LPS-lesioned SN. The beneficial effects of CAP were blocked by CZP, indicating TRPV1 involvement. The present data indicate that CAP regulated the M1 and M2 activation states of microglia/macrophage in the LPS-lesioned SN, which resulted in the survival of dopamine neurons. It is therefore likely that TRPV1 activation by CAP has therapeutic potential for treating neurodegenerative diseases, that are associated with neuroinflammation and oxidative stress, such as PD.

A drug that activates a neuron-protecting protein in the brain may help treat Parkinson’s disease (PD). Scientists believe neurons die during PD because of an over-activation of proinflammatory markers within immune cell populations, such as the microglia and macrophage cells found in the central nervous system and the brain. Now, Byung Kwan Jin at Kyung Hee University in Seoul and Won-Ho Shin at the Korea Institute of Toxicology in Daejeon and co-workers have demonstrated that a proinflammatory state can be reversed in rat PD models by administering capsaicin, an analgesic drug. Capsaicin activates a receptor protein that is highly expressed in neurons, microglia and astrocytes, and may play a role in neuronal function and motor control. The protein activation reversed the inflammatory state of the immune cells, providing a more protective environment for neurons.

In Vitro and In Vivo Characterization of Novel Stable Peptidic Ghrelin Analogs: Beneficial Effects in the Settings of Lipopolysaccharide-Induced Anorexia in Mice

Ghrelin, the only known orexigenic gut hormone produced primarily in the stomach, has lately gained attention as a potential treatment of anorexia and cachexia. However, its biologic stability is highly limited; therefore, a number of both peptide and nonpeptide ghrelin analogs have been synthesized. In this study, we provide in vitro and in vivo characterization of a series of novel peptide growth hormone secretagogue receptor (GHS-R1a) agonists, both under nonpathologic conditions and in the context of lipopolysaccharide (LPS)-induced anorexia. These analogs were based on our previous series modified by replacing the Ser³ with diaminopropionic acid (Dpr), the N-terminal Gly with sarcosine, and Phe⁴ with various noncoded amino acids. New analogs were further modified by replacing the n-octanoyl bound to Dpr³ with longer or unsaturated fatty acid residues, by incorporation of the second fatty acid residue into the molecule, or by shortening the peptide chain. These modifications preserved the ability of ghrelin analogs to bind to the membranes of cells transfected with GHS-R1a, as well as the GHS-R1a signaling activation. The selected analogs exhibited long-lasting and potent orexigenic effects after a single s.c. administration in mice. The stability of new ghrelin analogs in mice after s.c. administration was significantly higher when compared with ghrelin and [Dpr³]ghrelin, with half-lives of approximately 2 hours. A single s.c. injection of the selected ghrelin analogs in mice with LPS-induced anorexia significantly increased food intake via the activation of orexigenic pathways and normalized blood levels of proinflammatory cytokines, demonstrating the anti-inflammatory potential of the analogs.

Immune and metabolic alterations in first episode psychosis (FEP) patients

The molecular underpinnings associated to first episode psychosis (FEP) remains to be elucidated, but compelling evidence supported an association of FEP with blood alterations in biomarkers related to immune system, growth factors and metabolism regulators. Many of these studies have not been already confirmed in larger samples or have not considered the FEP diagnostic subgroups. In order to identify biochemical signatures of FEP, the serum levels of the growth factors BDNF and VEGF, the immune regulators IL-1RA, IL-6, IL-10 and IL-17, RANTES/CCL5, MIP-1b/CCL4, IL-8 and the metabolic regulators C-peptide, ghrelin, GIP, GLP-1, glucagon, insulin, leptin, PAI-1, resistin and visfatin were analysed in 260 subjects collected in the GET UP project. The results indicated an increase of MIP-1b/CCL4, VEGF, IL-6 and PAI-1, while IL-17, ghrelin, glucagon and GLP-1 were decreased in the whole sample of FEP patients (p < 0.01 for all markers except for PAI-1 p < 0.05). No differences were evidenced for these markers among the diagnostic groups that constitute the FEP sample, whereas IL-8 is increased only in patients with a diagnosis of affective psychosis. The principal component analysis (PCA) and variable importance analysis (VIA) indicated that MIP-1b/CCL4, ghrelin, glucagon, VEGF and GLP-1 were the variables mostly altered in FEP patients. On the contrary, none of the analysed markers nor a combination of them can discriminate between FEP diagnostic subgroups. These data evidence a profile of immune and metabolic alterations in FEP patients, providing new information on the molecular mechanism associated to the psychosis onset for the development of preventive strategies and innovative treatment targets.

Effect of interleukin-1β on ghrelin receptor in periodontal cells

OBJECTIVES

Periodontopathogens induce immunoinflammatory responses characterized by the release of inflammatory mediators, e.g., interleukin (IL)-1β, IL-6, and IL-8. Ghrelin (GHRL) is an appetite hormone which mediates its effect via the functional receptor GHS-R1a. This study was to examine the effect of an inflammatory insult on GHS-R1a in human periodontal cells.

MATERIALS AND METHODS

Periodontal ligament (PDL) cells and gingival fibroblasts (HGFs) were exposed to IL-1β in the presence and absence of GHRL. Cells were also pre-incubated with specific inhibitors of NF-κB or MEK1/MEK2 signaling. Gene expression of GHS-R1a and proinflammatory mediators was assessed by real-time PCR, GHS-R1 protein level by immunocytochemistry, and NF-κB nuclear translocation by immunofluorescence.

RESULTS

IL-1β increased significantly the GHS-R1a expression in both cell types in a dose-dependent manner. The stimulatory effect of IL-1β involved the NF-κB and MAPK pathways. Exposure of cells to IL-1β also resulted in an increased production of GHS-R1 protein in both cell types. Furthermore, GHRL counteracted significantly the stimulatory actions of IL-1β on IL-6 and IL-8 in PDL cells.

CONCLUSIONS

This study demonstrates for the first time that IL-1β upregulates the functional ghrelin receptor in periodontal fibroblastic cells. Moreover, these results further support the assumption that the GHRL/GHS-R system exerts anti-inflammatory effects. Therefore, the upregulation of ghrelin receptor in periodontal cells in response to an inflammatory stimulus may represent a negative feedback mechanism to attenuate the initial inflammatory process in periodontal diseases.

CLINICAL RELEVANCE

The anti-inflammatory GHRL/GHS-R system may serve as a promising target for the prevention and therapy of periodontal diseases.

Plasma ghrelin suppression as an early predictor for postoperative complications after pancreatoduodenectomy

BACKGROUND/OBJECTIVES

The gut peptide hormone ghrelin induces appetite and exhibits an anti-inflammatory effect. Serial perioperative changes in ghrelin have been examined in several surgical procedures, but few in pancreatectomy. The present study analyzed perioperative changes in plasma ghrelin levels after pancreaduodenectomy (PD).

METHODS

The study included 24 patients undergoing PD between May 2015 and January 2016 at Osaka University Hospital. Plasma ghrelin and interleukin-6 (IL-6) levels, as well as white blood cells (WBCs) and C-reactive protein (CRP), were measured preoperatively and on postoperative day (POD) 1, 3, 7, and 14 by enzyme-linked immunosorbent assay. The relationship between the individual ghrelin ratio relative to preoperative value (IGR) and the development of grade IIIa-V Clavien-Dindo (CD) complications was examined.

RESULTS

Twelve patients (50%) developed grade IIIa CD complications (n = 6 [25%] pancreatic fistula, n = 7 [29%] intraabdominal abscess, n = 3 [13%] post-pancreatectomy hemorrhage, n = 5 [21%] wound infection, and n = 1 [4%] lymphorrhea). The IGR on POD 1 was significantly lower (p = 0.014) in patients who developed the complications compared to those who did not, but no significant differences were found in terms of WBC, CRP, or IL-6 on POD 1. When the IGR cut-off was set to 82% by receiver operative curve analysis, the sensitivity was 83%, specificity 75% and area under the curve 0.80. The lower IGR group (≤82%) had more postoperative complications and longer hospital stay.

CONCLUSIONS

The IGR on POD 1 after PD is a useful marker for predicting postoperative complications.

Regulation of Ghrelin Receptor by Periodontal Bacteria In Vitro and In Vivo

Ghrelin plays a major role in obesity-related diseases which have been shown to be associated with periodontitis. This study sought to analyze the expression of the functional receptor for ghrelin (GHS-R1a) in periodontal cells and tissues under microbial conditions in vitro and in vivo. The GHS-R1a expression in human periodontal cells challenged with the periodontopathogen Fusobacterium nucleatum, in gingival biopsies from periodontally healthy and diseased individuals, and from rats with and without ligature-induced periodontitis was analyzed by real-time PCR, immunocytochemistry, and immunofluorescence. F. nucleatum induced an initial upregulation and subsequent downregulation of GHS-R1a in periodontal cells. In rat experimental periodontitis, the GHS-R1a expression at periodontitis sites was increased during the early stage of periodontitis, but significantly reduced afterwards, when compared with healthy sites. In human gingival biopsies, periodontally diseased sites showed a significantly lower GHS-R1a expression than the healthy sites. The expression of the functional ghrelin receptor in periodontal cells and tissues is modulated by periodontal bacteria. Due to the downregulation of the functional ghrelin receptor by long-term exposure to periodontal bacteria, the anti-inflammatory actions of ghrelin may be diminished in chronic periodontal infections, which could lead to an enhanced periodontal inflammation and tissue destruction.

Therapeutic Potential of Targeting the Ghrelin Pathway

Ghrelin was discovered in 1999 as the endogenous ligand of the growth-hormone secretagogue receptor 1a (GHSR1a). Since then, ghrelin has been found to exert a plethora of physiological effects that go far beyond its initial characterization as a growth hormone (GH) secretagogue. Among the numerous well-established effects of ghrelin are the stimulation of appetite and lipid accumulation, the modulation of immunity and inflammation, the stimulation of gastric motility, the improvement of cardiac performance, the modulation of stress, anxiety, taste sensation and reward-seeking behavior, as well as the regulation of glucose metabolism and thermogenesis. Due to a variety of beneficial effects on systems’ metabolism, pharmacological targeting of the endogenous ghrelin system is widely considered a valuable approach to treat metabolic complications, such as chronic inflammation, gastroparesis or cancer-associated anorexia and cachexia. The aim of this review is to discuss and highlight the broad pharmacological potential of ghrelin pathway modulation for the treatment of anorexia, cachexia, sarcopenia, cardiopathy, neurodegenerative disorders, renal and pulmonary disease, gastrointestinal (GI) disorders, inflammatory disorders and metabolic syndrome.

The neurological effects of ghrelin in brain diseases: Beyond metabolic functions

Ghrelin, a peptide released by the stomach that plays a major role in regulating energy metabolism, has recently been shown to have effects on neurobiological behaviors. Ghrelin enhances neuronal survival by reducing apoptosis, alleviating inflammation and oxidative stress, and accordingly improving mitochondrial function. Ghrelin also stimulates the proliferation, differentiation and migration of neural stem/progenitor cells (NS/PCs). Additionally, the ghrelin is benefit for the recovery of memory, mood and cognitive dysfunction after stroke or traumatic brain injury. Because of its neuroprotective and neurogenic roles, ghrelin may be used as a therapeutic agent in the brain to combat neurodegenerative disease. In this review, we highlight the pre-clinical evidence and the proposed mechanisms underlying the role of ghrelin in physiological and pathological brain function.

The gut reaction to traumatic brain injury

Traumatic brain injury (TBI) is a complex disorder that affects millions of people worldwide. The complexity of TBI partly stems from the fact that injuries to the brain instigate non-neurological injuries to other organs such as the intestine. Additionally, genetic variation is thought to play a large role in determining the nature and severity of non-neurological injuries. We recently reported that TBI in flies, as in humans, increases permeability of the intestinal epithelial barrier resulting in hyperglycemia and a higher risk of death. Furthermore, we demonstrated that genetic variation in flies is also pertinent to the complexity of non-neurological injuries following TBI. The goals of this review are to place our findings in the context of what is known about TBI-induced intestinal permeability from studies of TBI patients and rodent TBI models and to draw attention to how studies of the fly TBI model can provide unique insights that may facilitate diagnosis and treatment of TBI.

Ghrelin protects MES23.5 cells against rotenone via inhibiting mitochondrial dysfunction and apoptosis

Ghrelin is an endogenous ligand for the growth hormone secretagogue (GHS) receptor and has several important physiological functions. Recently, particular attention has been paid to its neuroprotective effect. Rotenone is used to investigate the pathogenesis of Parkinson's disease (PD) for its ability to inhibit mitochondrial complex I. The current study was carried out to investigate the neuroprotective effects of ghrelin against rotenone in MES 23.5 dopaminergic cells and explored the possible mechanisms underlying this protection. Our results showed that rotenone induced significant decrease in cell viability which was counteracted by ghrelin treatment. In addition, rotenone challenge reduced mitochondrial membrane potential, inhibited the activity of mitochondrial complex I and depressed cytochrome C release from mitochondria. This mitochondrial dysfunction was reversed by ghrelin treatment. Furthermore, our results demonstrated that ghrelin protected MES23.5 cells against rotenone-induced apoptosis by inhibiting activation of caspase-3. Overall, our findings showed ghrelin provided protective effects on MES23.5 dopaminergic cells against rotenone via restoring mitochondrial dysfunction and inhibiting mitochondrial dependent apoptosis.

Acylated but not des-acyl ghrelin is neuroprotective in an MPTP mouse model of Parkinson's disease

The gut hormone ghrelin is widely beneficial in many disease states. However, ghrelin exists in two distinctive isoforms, each with its own metabolic profile. In Parkinson's Disease (PD) acylated ghrelin administration is neuroprotective, however, the role of des-acylated ghrelin remains unknown. In this study, we wanted to identify the relative contribution each isoform plays using the MPTP model of PD. Chronic administration of acylated ghrelin in mice lacking both isoforms of ghrelin (Ghrelin KO) attenuated the MPTP-induced loss on tyrosine hydroxylase (TH) neuronal number and volume and TH protein expression in the nigrostriatal pathway. Moreover, acylated ghrelin reduced the increase in glial fibrillary acidic protein and Ionized calcium binding adaptor molecule 1 microglia in the substantia nigra. However, injection of acylated ghrelin also elevated plasma des-acylated ghrelin, indicating in vivo deacetylation. Next, we chronically administered des-acylated ghrelin to Ghrelin KO mice and observed no neuroprotective effects in terms of TH cell number, TH protein expression, glial fibrillary acidic protein and ionized calcium binding adaptor molecule 1 cell number. The lack of a protective effect was mirrored in ghrelin-O-acyltransferase KO mice, which lack the ability to acylate ghrelin and consequently these mice have chronically increased plasma des-acyl ghrelin. Plasma corticosterone was elevated in ghrelin-O-acyltransferase KO mice and with des-acylated ghrelin administration. Overall, our studies suggest that acylated ghrelin is the isoform responsible for in vivo neuroprotection and that pharmacological approaches preventing plasma conversion from acyl ghrelin to des-acyl ghrelin may have clinical efficacy to help slow or prevent the debilitating effects of PD. Ghrelin exists in the plasma as acyl and des-acyl ghrelin. We determined the form responsible for in vivo neuroprotection in a mouse model of Parkinson's disease. Although exogenous acyl ghrelin is deacylated in situ to des-acyl, only acyl ghrelin was neuroprotective by attenuating dopamine cell loss and glial activation. Acyl ghrelin is a therapeutic option to reduce Parkinson's Disease progression. Cover Image for this issue: doi: 10.1111/jnc.13316.

Short-term calorie restriction enhances adult hippocampal neurogenesis and remote fear memory in a Ghsr-dependent manner

The beneficial effects of calorie restriction (CR) have been described at both organismal and cellular levels in multiple organs. However, our understanding of the causal mediators of such hormesis is poorly understood, particularly in the context of higher brain function. Here, we show that the receptor for the orexigenic hormone acyl-ghrelin, the growth hormone secretagogue receptor (Ghsr), is enriched in the neurogenic niche of the hippocampal dentate gyrus (DG). Acute elevation of acyl-ghrelin levels by injection or by overnight CR, increased DG levels of the neurogenic transcription factor, Egr-1. Two weeks of CR increased the subsequent number of mature newborn neurons in the DG of adult wild-type but not Ghsr(-/-) mice. CR wild-type mice also showed improved remote contextual fear memory. Our findings suggest that Ghsr mediates the beneficial effects of CR on enhancing adult hippocampal neurogenesis and memory.

One-day high-fat diet induces inflammation in the nodose ganglion and hypothalamus of mice

A high-fat diet (HFD) induces inflammation in systemic organs including the hypothalamus, resulting in obesity and diabetes. The vagus nerve connects the visceral organs and central nervous system, and the gastric-derived orexigenic peptide ghrelin transmits its starvation signals to the hypothalamus via the vagal afferent nerve. Here we investigated the inflammatory response in vagal afferent neurons and the hypothalamus in mice following one day of HFD feeding. This treatment increased the number of macrophages/microglia in the nodose ganglion and hypothalamus. Furthermore, one-day HFD induced expression of Toll-like receptor 4 in the goblet cells of the colon and upregulated mRNA expressions of the proinflammatory biomarkers Emr1, Iba1, Il6, and Tnfα in the nodose ganglion and hypothalamus. Both subcutaneous administration of ghrelin and celiac vagotomy reduced HFD-induced inflammation in these tissues. HFD intake triggered inflammatory responses in the gut, nodose ganglion, and subsequently in the hypothalamus within 24 h. These findings suggest that the vagal afferent nerve may transfer gut-derived inflammatory signals to the hypothalamus via the nodose ganglion, and that ghrelin may protect against HFD-induced inflammation.

Differential effects of lipopolysaccharide on energy metabolism in murine microglial N9 and cholinergic SN56 neuronal cells

There are significant differences between acetyl-CoA and ATP levels, enzymes of acetyl-CoA metabolism, and toll-like receptor 4 contents in non-activated microglial N9 and non-differentiated cholinergic SN56 neuroblastoma cells. Exposition of N9 cells to lipopolysaccharide caused concentration-dependent several-fold increases of nitrogen oxide synthesis, accompanied by inhibition of pyruvate dehydrogenase complex, aconitase, and α-ketoglutarate dehydrogenase complex activities, and by nearly proportional depletion of acetyl-CoA, but by relatively smaller losses in ATP content and cell viability (about 5%). On the contrary, SN56 cells appeared to be insensitive to direct exposition to high concentration of lipopolysaccharide. However, exogenous nitric oxide resulted in marked inhibition pyruvate dehydrogenase and aconitase activities, depletion of acetyl-CoA, along with respective loss of SN56 cells viability. These data indicate that these two common neurodegenerative signals may differentially affect energy-acetyl-CoA metabolism in microglial and cholinergic neuronal cell compartments in the brain. Moreover, microglial cells appeared to be more resistant than neuronal cells to acetyl-CoA and ATP depletion evoked by these neurodegenerative conditions. Together, these data indicate that differential susceptibility of microglia and cholinergic neuronal cells to neurotoxic signals may result from differences in densities of toll-like receptors and degree of disequilibrium between acetyl-CoA provision in mitochondria and its utilization for energy production and acetylation reactions in each particular group of cells. There are significant differences between acetyl-CoA and ATP levels and enzymes of acetyl-CoA metabolism in non-activated microglial N9 and non-differentiated cholinergic SN56 neuroblastoma cells. Pathological stimulation of microglial toll-like receptors (TLRs) triggered excessive synthesis of microglia-derived nitric oxide (NO)/NOO radicals that endogenously inhibited pyruvate dehydrogenase complex (PDHC), aconitase, and α-ketoglutarate dehydrogenase complex. However, it caused none or small suppressions of acetyl-CoA and microglial viability, respectively. Microglia-derived NO inhibited same enzymes in cholinergic neuronal cells causing marked viability loss because of acetyl-CoA deficits evoked by its competitive consumption by energy producing and acetylcholine/N-acetyl-l-aspartate (NAA) synthesizing pathways.

Hormonal protection in acute pancreatitis by ghrelin, leptin and melatonin

Acute pancreatitis is a nonbacterial disease of the pancreas. The severe form of this ailment is characterized by high mortality. Whether acute pancreatitis develops as the severe type or resolves depends on the intensity of the inflammatory process which is counteracted by the recruitment of innate defense mechanisms. It has been shown that the hormones ghrelin, leptin and melatonin are able to modulate the immune function of the organism and to protect the pancreas against inflammatory damage. Experimental studies have demonstrated that the application of these substances prior to the induction of acute pancreatitis significantly attenuated the intensity of the inflammation and reduced pancreatic tissue damage. The pancreatic protective mechanisms of the above hormones have been related to the mobilization of non-specific immune defense, to the inhibition of nuclear factor kappa B and modulation of cytokine production, to the stimulation of heat shock proteins and changes of apoptotic processes in the acinar cells, as well as to the activation of antioxidant system of the pancreatic tissue. The protective effect of ghrelin seems to be indirect and perhaps dependent on the release of growth hormone and insulin-like growth factor 1. Leptin and ghrelin, but not melatonin, employ sensory nerves in their beneficial action on acute pancreatitis. It is very likely that ghrelin, leptin and melatonin could be implicated in the natural protection of the pancreatic gland against inflammatory damage because the blood levels of these substances increase in the initial phase of pancreatic inflammation. The above hormones could be a part of the innate resistance system which might remove noxious factors and could suppress or attenuate the inflammatory process in the pancreas.

Recombinant Wnt3a and Wnt5a elicit macrophage cytokine production and tolerization to microbial stimulation via Toll-like receptor 4

An increasing number of studies address the roles of Wnt proteins in shaping leukocyte functions. Recombinant Wnt3a and Wnt5a, prototypical activators of β-Catenin-dependent and -independent Wnt signaling, respectively, are widely used to investigate the effects of Wnt proteins on myeloid cell functions. Recent reports describe both proinflammatory and immunemodulatory effects of Wnt3a and Wnt5a on macrophages, DCs, and microglia. The underlying molecular mechanisms for this divergence are unclear. We show here that recombinant Wnt3a- and Wnt5a-induced cytokine production from murine C57BL/6 macrophages was dependent on TLR4 and inhibited by Polymyxin B. Similarly, impairment of TLR-induced cytokine production upon preexposure to Wnt proteins was TLR4 dependent. The extent of Wnt3a- and Wnt5a-induced inflammatory gene expression greatly varied between Wnt protein lots. We conclude that cytokine responses and TLR tolerization induced by recombinant Wnt proteins are likely explained by contaminating TLR4 agonists, although we cannot fully exclude that Wnt proteins have an intrinsic capacity to signal via TLR4. This study emphasizes the need for careful, independent verification of Wnt-mediated cellular responses.